This invention relates to a method of producing an electro-optical device applied as an image display device to drive an electro-optical material layer by making use of plasma, thus to carry out selection of pixels.
As the means for allowing, e.g., a liquid crystal display to have high resolution and high contrast, there is generally carried out a method in which active elements such as transistors, etc. are provided for every display pixel, to drive them (which method is so called an active matrix addressing system).
In this case, however, since it is necessary to provide a large number of semiconductor elements such as thin film transistors, the problem of yield is apprehended particularly when the display area is enlarged, giving rise to the great problem that the cost is necessarily increased.
Thus, as the means for solving this, Buzaku et al. have proposed in the Japanese Laid Open Application No. 217396/89 publication a method utilizing discharge plasma in place of semiconductor elements such as MOS transistors or thin film transistors, etc. as an active element.
The configuration of an image display device for driving a liquid crystal by making use of discharge plasma will be briefly described.
This image display device is called a plasma addressed liquid crystal display device (PALC), and is of a structure in which, as shown in FIG. 7, a liquid crystal layer 101 serving as an electro-optical material layer and plasma chambers 102 are adjacently arranged through a thin dielectric sheet 103 comprised of glass, etc.
The plasma chambers 102 are constituted by forming a plurality of grooves 105 in parallel to each other in a glass substrate or base plate 104. Within these chambers, ionizable gas is filled. Accordingly, projecting portions 105a between respective grooves 105 perform a role as a partition wall partitioning the plasma chamber 102, and also perform a role as a gap spacer for each plasma chamber 102.
Further, pairs of electrodes 106 and 107 in parallel to each other are provided at respective grooves 105. These electrodes 106 and 107 function as an anode and a cathode for ionizing gas within the plasma chambers 102 to generate discharge plasma.
On the other hand, the liquid crystal layer 101 is held by the dielectric sheet 103 and a transparent substrate 108. On the surface at the liquid crystal layer 101 side of the transparent substrate 108, transparent electrodes 109 are formed. These transparent electrodes 109 are perpendicular to the plasma chambers constituted by the grooves 105. The portions where the transparent electrodes 109 and the plasma chambers 102 intersect with each other correspond to respective pixels.
In the above-mentioned image display device, by switching and scanning in sequence the plasma chambers 102 where plasma discharge is carried out, and applying signal voltages to the transparent electrodes 109 on the liquid crystal layer 101 side in synchronism with the switching scan operation, these signal voltages are held by respective pixels. The liquid crystal layer 101 is thus driven.
Accordingly, the grooves 105, i.e., plasma chambers 102 respectively correspond to one scanning lines, and the discharge region is divided every scanning unit.
Meanwhile, in an image display device utilizing discharge plasma as described above, it is considered that unenlarged display area is more easily realized than in an image display device using semiconductor elements. However, various problems are left in putting such an image display device into practice.
Particularly, when attention is drawn to the manufacturing thereof, many problems are involved in handling an extremely thin dielectric sheet (glass sheet), and the following problems further arise.
(1) A dielectric sheet of a thickness to such an extent used here (approximately 50 .mu.m) has great unevenness in the thickness, resulting in unevenness in the characteristic. Further, it is very difficult to implement a post-processing for eliminating unevenness in the thickness.
(2) When attention is drawn to an electrical coupling between the electro-optical material layer and the discharge region, it is desirable that the dielectric sheet is as thin as possible, but it is difficult to prepare an extremely thin dielectric sheet in manufacturing.
(3) In the case of an extremely thin dielectric sheet, it is impossible to prepare a considerably large dielectric sheet because of the problem of strength, thus making it difficult to provide an enlarged display screen.
(4) In the case of sealing a dielectric sheet on a glass substrate provided with grooves, heat processing such as frit seal, etc. is required, giving rise to the problem of cracking or shrivelling, etc.